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Strings and Music
Strings and Music Have you ever wondered how sound is created from a guitar, or any other string instrument? Well, in order for music and sound to be created from a string instrument, string must be present. A string is the element, and source of vibration in string instruments. Strings The string plays a huge role in creating the sound from a string instrument. In string instruments, the strings may be "plain strings," made up of only one material, such as steel or nylon, or they may be "wound strings," with a core of one material with other materials winding around the core to increase the mass and thickness of the string. In order to get the strings to vibrate, they are kept under a tension that allows them to move freely. String Length picture from: http://www.howstuffworks.com In general, ~ the shorter the string, the higher the note. ~ the higher the tension, the higher the note. ~ the lighter the string, the higher the note. Harmonics As shown above, the strings are almost completely fixed at both ends, creating nodes at both ends. When a string is plucked, or moved in some way, the nodes limits the ways and frequencies of the string, creating standing waves. For example, if your basic string (wavelength=L) was plucked, it could allow a multitude of possibilities of creating antinodes in the center. A harmonic is the frequency of the vibrating string, and the sound it creates. Because all waves in a string travel with the same speed, the frequency changes, as shown in the equation. All the different frequencies are called a harmonic series. If we were to find the frequencies of these possibilities, we can see a pattern forming. The frequency of a wave is found by dividing the velocity by the wavelength. The original wavelength, forms the first frequency, otherwise known as the fundamental frequency. After the fundamental frequency, you can find the frequencies for all other harmonics. The fundamental has frequency f1 = v/wavelength = v/2L, The second harmonic has frequency f2 = v/L2 = 2v/2L = 2f1, The third harmonic has frequency f3 = v/L3 = 3v/2L = 3f1, The fourth harmonic has frequency f4 = v/L4 = 4v/2L = 4f1, and, to generalize, The nth harmonic has frequency fn = v/Ln = nv/2L = nf1. Music Music is the sound that most people recognize as the constant sound of vibrating sound waves. Sound Waves In the simplest case, a sine wave can be viewed as a sound wave. This sine wave causes the air pressure to increase and decrease, causing a "pure tone." Pure tones can be produced through tuning forks or whistling. The rate at which the air pressure fluctuates controls the frequency of the tone, which is measured in oscillations per second, or hertz. The frequency also helps determine the pitch of the note being played. Whenever two different pitches are played at the same time, their sound waves interact with each other, and the differences in the air pressure creating a new sound wave. Sound Production On it's own, a vibrating string creates a very quiet sound, so string instruments are usually constructed in a way that the noise from the vibrating string goes to a hollow resonating chamber, a soundboard, or both. The hollow resonating chamber and the soundboard both pick up the quieter noise from the vibration, and make it louder. The strings' vibrations are distributed through the bridge and soundpost to all the surfaces of the instrument, and are therefore louder. It is often said that the soundboard "amplifies" the sound of the strings. Technically speaking, no amplification occurs, since all of the energy to produce the sound comes from the original vibrating strings. What really happens is that the soundboard of the instrument provides a larger surface area to create sound waves than that of the string, so the larger surface area moves more air, and results in a louder sound. References The University of New South Wales How Stuff Works The Physics of Music Harmonics Vibrating Strings Resources Physics Classroom This website will help you if you have any further questions about strings or music. String Instruments This website will help you find out more information if you have any other questions on how string instruments work. String This website has more information about strings. Musical Strings This website has information that's specific to strings used in musical instruments. Harmonics This website explains harmonics in more in depth description.